docs: def uniprot_ec(uniprot_id):
      """Retrieve the EC number annotation for a UniProt ID.
  
      Args:
          uniprot_id: Valid UniProt ID
  
      Returns:
  
      """
      r = requests.post('http://www.uniprot.org/uniprot/?query=%s&columns=ec&format=tab' % uniprot_id)
      ec = r.content.decode('utf-8').splitlines()[1]
  
      if len(ec) == 0:
          ec = None
  
      return ec